Colossus code-breaking computer marks its 70th birthday

The machine was designed and built to decode the Lorenz encrypted messages sent between Hitler and his most senior soldiers. A rebuilt version of the machine now resides in the National Museum of Computing (TNMOC) at Bletchley Park.

During World War II there were 10 Colossus machines based at Bletchley Park, each housing 2,500 valves that were used to decrypt messages that it is widely thought shortened the war by a matter of months or even years.

The rebuilt Colossus is a Mark II machine completed in 2012 from fragments of the original plans coupled with memories of veterans who worked on the project, some of whom were present at todays celebrations.

Once the information was declassified in 1975 it became apparent that most of the machines had been broken up and the plans destroyed as a subterfuge to hide the fact that they were still being used to monitor Soviet communications long after the war.

Demonstrations of code-breaking using the machine will take place, along with a chance for veterans and their decendents to meet and greet the public, including machine operators, maintenance staff and designers.